In the past, data in the form of a barcode was recorded in a BCA (burst cutting area) in the innermost peripheral part of an optical disk in order to prevent the illegal copying of the optical disk. This barcode data included a serial number, an identification number, or other such individual information, and this information was used to manage optical disks and prevent their illegal copying.
The BCA code (barcode data) is made up of a plurality of bars arranged with varying spacing and includes data generated by converting BCA data by means of specific data conversion. BCA data is the original data of the BCA code, and is individual information consisting of a serial number, an identification number, or the like.
In the process of manufacturing a phase-change optical disk that differentiates data in a crystalline state on a recording surface, the optical disk undergoes sputtering or the like, after which the recording surface becomes amorphous, which is a form with low reflectivity. Therefore, a step is necessary to crystallize the recording layer (hereinafter also referred to as initialization) in order to make it possible for data to be recorded. Also, a BCA code is recorded at the stage of manufacturing the optical disk. In view of this, it has been proposed that the optical disk initialization step be performed continuously with the recording of the BCA code. For example, a BCA code is recorded by irradiating a specific radial region with a laser beam in a pulse pattern to produce initialized sites (high reflectivity sites) and non-initialized sites (low reflectivity sites), and initialization is performed in the other radial region by irradiation with a laser beam of a specific intensity.
The recording of the BCA code is carried out as follows, for example. When the optical disk is rotated while moving the laser beam irradiation position in the radial direction, the elliptical beam spot directed at the optical disk moves in the radial direction and the peripheral direction of the optical disk. The parts of the optical disk where the laser beam intensity is high undergo initialization and take on a high reflectivity, while the parts where the laser beam intensity is low remain as bars with low reflectivity. The pulsed laser beam emission timing is controlled with respect to the rotation of the optical disk so that sites of high and low reflectivity in the peripheral direction are formed at the same radial positions. This allows bar-shaped BCA code to be recorded in a specific radial region of the optical disk.
Initialization is performed in the inner peripheral region of an optical disk adjacent to an inner periphery of the radial region in which the BCA code is recorded, and in the outer peripheral region that is adjacent to an outer periphery of the radial region in which the BCA code is recorded. Therefore, while the beam spot is moved from the inner peripheral side to the outer peripheral side of the optical disk, first the inner peripheral region adjacent to the radial region in which the BCA code is to be recorded is initialized, and then the BCA code is recorded in the radial region in which the BCA code is to be recorded, and then the outer peripheral region adjacent to the radial region in which the BCA code is recorded is initialized.
There is a known apparatus with which the radial positions of the inner peripheral end and the outer peripheral end of each BCA code are aligned in the peripheral direction in the recording of BCA code (Japanese Laid-Open Patent Application 2009-129505, for example).